Wed·Oct 27, 2021Wednesday·October 27, 2021

1. 01*

   Parton distributions in the SMEFT from high-energy Drell-Yan tails

   Maeve Madigan🇬🇧 · James Moore🇬🇧

   We present a study of the interplay between PDF and EFT effects in high-mass Drell-Yan at the LHC. We quantify the impact of a consistent joint determination of the PDFs and Wilson coefficients on the bounds obtained on the EFT and examine the effect on the PDFs, determining the extent to which EFT signals could be reabsorbed into the large-$x$ quark and anti-quark PDFs. Finally, we present dedicated projections for the High-Luminosity LHC and evaluate its ultimate potential to constrain the EFT parameters, while taking into account potential modifications of the proton structure.

   hep-phPoS(2022)·9 citations
2. 02*

   Probing Lorentz Invariance Violation with Atmospheric Neutrinos at INO-ICAL

   Sadashiv Sahoo🇮🇳 · Anil Kumar🇮🇳 · Sanjib Kumar Agarwalla🇮🇳

   The possibility of Lorentz Invariance Violation (LIV) may appear in unified theories, such as string theory, which allow the existence of a new space-time structure at the Planck scale ($M_p\sim 10^{19}$ GeV). This effect can be observed at low energies with a strength of $\sim 1/M_p$ using the perturbative approach. In the minimal Standard Model extension (SME) framework, the neutrino mass-induced flavor oscillation gets modified in the presence of LIV. The Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) offers a unique window to probe these LIV parameters by observing atmospheric neutrinos and antineutrinos separately over a wide range of baselines in the multi-GeV energy range. In this paper, for the first time, we study in detail how the CPT-violating LIV parameters $(a_{\mu \tau },a_{e\mu },a_{e\tau })$ can alter muon survival probabilities and expected ${\mu }^{-}$ and ${\mu }^{+}$ event rates at ICAL. Using 500 kt$\cdot$yr exposure of ICAL, we place stringent bounds on these CPT-violating LIV parameters at 95\% C.L., which are slightly better than the present Super-Kamiokande limits. We demonstrate the advantage of incorporating hadron energy information and charge identification capability at ICAL while constraining these LIV parameters. Further, the impact of the marginalization over the oscillation parameters and choice of true values of ${\sin }^2{\theta }_{23}$ on LIV constraints is described. We also study the impact of these LIV parameters on mass ordering determination and precision measurement of atmospheric oscillation parameters.

   hep-phhep-exphysics.ins-detJHEP(2022)·25 citations
3. 03*

   Exotic Higgs Decays to Four Taus at Future Electron-Positron Colliders

   Jessie Shelton🇺🇸 · Dong Xu🇺🇸

   We study the prospects for the exotic Higgs decay mode $h\to ss\to 4\tau$ at planned electron-positron colliders in the case where the beyond-the-Standard Model particle $s$ is too light to decay into $b\bar{b}$ pairs. We find that with 5 ab${}^{-1}$ of unpolarized collisions at 240 GeV, the branching ratio into this final state can be constrained to be below $\sim 1.3\times 10^{-4}$ at 95\% CL, depending on the mass of $s$ and the assumed tracking efficiency.

   hep-ph7 citations
4. 04*

   Two-loop Prediction of the Anomalous Magnetic Moment of the Muon in the Two-Higgs Doublet Model with GM2Calc 2

   Peter Athron🇨🇳 · Csaba Balazs🇦🇺 · Adriano Cherchiglia🇧🇷 · Douglas H.J. Jacob🇦🇺 · Dominik Stöckinger🇩🇪 · Hyejung Stöckinger-Kim🇩🇪 · Alexander Voigt🇩🇪

   We present an extension of the GM2Calc software to calculate the muon anomalous magnetic moment ($a_{\mu }^{\text{BSM}}$) in the Two-Higgs Doublet Model. The Two-Higgs Doublet Model is one of the simplest and most popular extensions of the Standard Model. It is one of the few single field extensions that can give large contributions to $a_{\mu }^{\text{BSM}}$. It is essential to include two-loop corrections to explain the long standing discrepancy between the Standard Model prediction and the experimental measurement in the Two-Higgs Doublet Model. The new version GM2Calc 2 implements the state of the art two-loop calculation for the general, flavour violating Two-Higgs Doublet Model as well as for the flavour aligned Two-Higgs Doublet Model and the type I, II, X and Y flavour conserving variants. Input parameters can be provided in either the gauge basis or the mass basis, and we provide an easy to use SLHA-like command-line interface to specify these. Using this interface users may also select between Two-Higgs Doublet Model types and choose which contributions to apply. In addition, GM2Calc 2 also provides interfaces in C++, C, Python and Mathematica, to make it easy to interface with other codes.

   hep-phEPJC(2022)·23 citations
5. 05*

   $B$ Flavour Anomalies: 2021 Theoretical Status Report

   David London🇨🇦 · Joaquim Matias🇪🇸

   At the present time, there are discrepancies with the predictions of the SM in several observables involving $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to c{\ell }^{-}{\bar{\nu }}_{\ell }$ decays. These are the $B$ flavour anomalies. In this review, we summarize the data as of Moriond 2021 and present theoretical new-physics explanations from both a model-independent effective-field-theory point of view and through the building of explicit models. Throughout, we stress the complementarity of these two approaches. We also discuss combined explanations of both $B$ anomalies, and present models that also explain other problems, such as dark matter, $(g-2{)}_{\mu }$, neutrino properties, and hadronic anomalies.

   hep-phAnn.Rev.Nucl.Part.Sci.(2022)·129 citations
6. 06*

   Three-Loop Corrections to Lamb Shift in Muonium and Positronium

   Michael I. Eides🇺🇸 · Valery A. Shelyuto🇷🇺

   We calculate hard spin-independent three-loop radiative corrections to energy levels in muonium and positronium which are due to radiative insertions in two-photon exchange diagrams. These corrections could be relevant for the new generation of precise $1S-2S$ and $2S-2P$ measurements in muonium and positronium.

   hep-phphysics.atom-phPRA(2022)·18 citations
7. 07*

   Large Hadron Collider Constraints on Some Simple $Z^{\prime }$ Models for $b\to s{\mu }^{+}{\mu }^{-}$ Anomalies

   B.C. Allanach🇬🇧 · J. M. Butterworth🇬🇧 · Tyler Corbett🇩🇰

   We examine current Large Hadron Collider constraints on some simple $Z^{\prime }$ models that significantly improve on Standard Model fits to $b\to s{\mu }^{+}{\mu }^{-}$ transition data. The models that we consider are the 'third family baryon number minus second family lepton number' $(B_3-L_2)$ model and the 'third family hypercharge' model and variants. The constraints are applied on parameter regions of each model that fit the $b\to s{\mu }^{+}{\mu }^{-}$ transition data and come from high-mass Drell-Yan di-muons and measurements of Standard Model processes. This latter set of observables place particularly strong bounds upon the parameter space of the $B_3-L_2$ model when the mass of the $Z^{\prime }$ boson is less than 300 GeV.

   hep-phhep-exEPJC(2021)·26 citations
8. 08*

   Short-distance constraints in hadronic-light-by-light for the muon $g-2$

   Johan Bijnens🇸🇪 · Nils Hermansson-Truedsson🇨🇭 · Antonio Rodríguez Sánchez🇫🇷

   In this talk recent progress in studying the short-distance properties of the hadronic light-by-light contribution to the muon $g-2$ is described. The intermediate and short-distance part is a major contributor to the error of the theoretical prediction as described in the recent white paper [1]. We have shown that the massless quark-loop is the first term in a systematic expansion at short-distances, a result already used in the white paper. Newer results conclude that both nonperturbative and perturbative corrections are under control. The talk describes these developments and how they fit in the total theoretical prediction for the muon $g-2$.

   hep-phPoS(2024)·1 citation
9. 09*

   $B$ anomalies and muon $g-2$ from Dark Matter

   Giorgio Arcadi🇮🇹 · Lorenzo Calibbi🇨🇳 · Marco Fedele🇩🇪 · Federico Mescia🇪🇸

   Motivated by the result of the Muon g-2 experiment and the long-standing anomalies in semileptonic $B$ meson decays, we systematically build a class of minimal models that can address both experimental results thanks to the contributions of a set of new fields that include a thermal Dark Matter candidate.

   hep-phPoS(2022)·1 citation
10. 10*

    Novel Corrections to the Momentum Sum Rule for Nuclear Structure Functions

    Stanley J. Brodsky🇺🇸 · Valery E. Lyubovitskij🇩🇪 · Ivan Schmidt🇨🇱

    We address novel features of deep inelastic lepton scattering on nuclei at small Bjorken variable $x_{Bj}$. In this regime the lepton-nuclear cross section involves the interference between the standard lepton-quark scattering amplitude for the deep inelastic scattering (DIS) process on a single nucleon and a two-step process where diffractive scattering on a first nucleon combines with the amplitude for DIS on a second nucleon. The phases associated with the $t$-channel exchanges to the diffractive amplitude can produce either a destructive or constructive quantum-mechanical interference of the one-step and two-step amplitudes. This provides a mechanism regulating the respective amounts of shadowing suppression and anti-shadowing enhancement at low $x_{Bj}$. Furthermore, the standard leading-twist operator product and handbag diagram analyses of the forward virtual Compton amplitude on the nucleus are inapplicable, barring a conventional probabilistic interpretation. A main observable consequence is the impossibility of extracting momentum and spin sum rules from nuclear structure functions. We present numerical predictions supporting this picture and test them against DIS neutrino-nucleus and charged-lepton-nucleus scattering data.

    hep-phPLB(2022)·6 citations
11. 11*

    Deep Learning Exotic Hadrons

    JPAC Collaboration: L. Ng🇺🇸 · L. Bibrzycki🇵🇱 · J. Nys🇨🇭 · C. Fernandez-Ramirez🇲🇽 · A. Pilloni🇮🇹 · V. Mathieu🇪🇸 · A.J. Rasmusson🇺🇸 · A.P. Szczepaniak🇺🇸

    We perform the first model independent analysis of experimental data using Deep Neural Networks to determine the nature of an exotic hadron. Specifically, we study the line shape of the $P_c(4312)$ signal reported by the LHCb collaboration and we find that its most likely interpretation is that of a virtual state. This method can be applied to other near-threshold resonance candidates.

    hep-phhep-exnucl-thPRD(2022)·30 citations
12. 12*

    Coupled-channel approach to $T_{cc}^{+}$ including three-body effects

    Meng-Lin Du🇪🇸 · Vadim Baru🇩🇪 · Xiang-Kun Dong🇨🇳 · Arseniy Filin🇩🇪 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Alexey Nefediev🇷🇺 · Juan Nieves🇪🇸 · Qian Wang🇨🇳

    A coupled-channel approach is applied to the charged tetraquark state $T_{cc}^{+}$ recently discovered by the LHCb Collaboration. The parameters of the interaction are fixed by a fit to the observed line shape in the three-body $D^0{D}^0{\pi }^{+}$ channel. Special attention is paid to the three-body dynamics in the $T_{cc}^{+}$ due to the finite life time of the $D^{\ast }$. An approach to the $T_{cc}^{+}$ is argued to be self-consistent only if both manifestations of the three-body dynamics, the pion exchange between the $D$ and $D^{\ast }$ mesons and the finite $D^{\ast }$ width, are taken into account simultaneously to ensure that three-body unitarity is preserved. This is especially important to precisely extract the pole position in the complex energy plane whose imaginary part is very sensitive to the details of the coupled-channel scheme employed. The $D^0{D}^0$ and $D^0{D}^{+}$ invariant mass distributions, predicted based on this analysis, are in good agreement with the LHCb data. The low-energy expansion of the $D^{\ast }D$ scattering amplitude is performed and the low-energy constants (the scattering length and effective range) are extracted. The compositeness parameter of the $T_{cc}^{+}$ is found to be close to unity, which implies that the $T_{cc}^{+}$ is a hadronic molecule generated by the interactions in the $D^{\ast +}{D}^0$ and $D^{\ast 0}{D}^{+}$ channels. Employing heavy-quark spin symmetry, an isoscalar $D^{\ast }{D}^{\ast }$ molecular partner of the $T_{cc}^{+}$ with $J^P=1^{+}$ is predicted under the assumption that the $D{D}^{\ast }$-$D^{\ast }{D}^{\ast }$ coupled-channel effects can be neglected.

    hep-phPRD(2022)·189 citations
13. 13*

    Masses and strong decays of open charm hexaquark states ${\Sigma }_c^{(\ast )}{\Sigma }_c^{(\ast )}$

    Xi-Zhe Ling🇨🇳 · Ming-Zhu Liu🇨🇳 · Li-Sheng Geng🇨🇳

    Inspired by the recent discovery of the doubly charmed tetraquark state $T_{cc}^{+}$ by the LHCb Collaboration, we perform a systematic study of masses and strong decays of open charm hexaquark states ${\Sigma }_c^{(\ast )}{\Sigma }_c^{(\ast )}$. Taking into account heavy quark spin symmetry breaking, we predict several bound states of isospin $I=0$, $I=1$, and $I=2$ in the one boson exchange model. Moreover, we adopt the effective Lagrangian approach to estimate the decay widths of ${\Sigma }_c^{(\ast )}{\Sigma }_c^{(\ast )}\to {\Lambda }_c{\Lambda }_c$ and their relevant ratios via the triangle diagram mechanism, which range from a few MeV to a few tens of MeV. We strongly recommend future experimental searches for the ${\Sigma }_c^{(\ast )}{\Sigma }_c^{(\ast )}$ hexaquark states in the ${\Lambda }_c{\Lambda }_c$ invariant mass distributions.

    hep-phEPJC(2021)·27 citations
14. 14*

    Detecting long-lived particles trapped in detector material at the LHC

    Jan Kieseler🇨🇭 · Juliette Alimena🇨🇭 · Jasmine Simms🇨🇭 · Thea Aarrestad🇨🇭 · Maurizio Pierini🇨🇭 · Alexander Kish🇺🇸

    We propose to implement a two-stage detection strategy for exotic long-lived particles that could be produced at the CERN LHC, become trapped in detector material, and decay later. The proposed strategy relies on an array of metal rods, combined to form a high-density target. In a first stage, the rods are exposed to radiation from LHC collisions in one of the experimental caverns. In a second stage, they are individually immersed in liquid argon in a different experimental hall, where out-of-time decays could produce a detectable signal. Using a benchmark case of long-lived gluino pair production, we show that this experiment would be sensitive to a wide range of masses. Such an experiment would have unique sensitivity to gluino-neutralino mass splittings down to 3 GeV, in previously uncovered particle lifetimes ranging from days to years.

    hep-phhep-exPRD(2022)·1 citation
15. 15*

    Reply to "Comment on 'Flavor invariants and renormalization-group equations in the leptonic sector with massive Majorana neutrinos'"

    Yilin Wang🇨🇳 · Bingrong Yu🇨🇳 · Shun Zhou🇨🇳

    In the preprint arXiv:2110.08210, some comments on our paper recently published in JHEP \textbf{09} (2021) 053 have been made. Since some of the comments are completely wrong and others are quite misleading, we decide to clarify the relevant issues in a formal reply. First of all, nothing is wrong about our calculations and physical results in the original paper. Second, there is no logical gap to fill at all. The fact that the $N$-dimensional unitary group over the field of complex numbers $\mathrm{U}(N,\mathbb{C})$ is not a linear algebraic group is actually irrelevant for the validity of the Molien-Weyl formula. As we shall explain in this reply, all the comments in arXiv:2110.08210 arise from the misunderstanding and misinterpretation of our discussions and results.

    hep-ph3 citations
16. 16*

    Axion Echos from the Supernova Graveyard

    Manuel A. Buen-Abad🇺🇸 · JiJi Fan🇺🇸 · Chen Sun🇮🇱

    Stimulated decays of axion dark matter, triggered by a source in the sky, could produce a photon flux along the continuation of the line of sight, pointing backward to the source. The strength of this so-called axion "echo" signal depends on the entire history of the source and could still be strong from sources that are dim today but had a large flux density in the past, such as supernova remnants (SNRs). This echo signal turns out to be most observable in the radio band. We study the sensitivity of radio telescopes such as the Square Kilometer Array (SKA) to echo signals generated by SNRs that have already been observed, and show that SKA could reach axion-photon couplings of order $g_{a\gamma \gamma }\sim \mathcal{O}(10^{-11}){\mathrm{GeV}}^{-1}$ for axion masses $m_a\lesssim 10^{-5}\mathrm{eV}$. In addition, we show projections of the detection reach for signals coming from old SNRs and from newly born supernovae that could be detected in the future. Intriguingly, an observable echo signal could come from old "ghost" SNRs which were very bright in the past but are now so dim that they haven't been observed.

    hep-phastro-ph.COastro-ph.GAastro-ph.HEPRD(2022)·29 citations
17. 17*

    Axion dark matter-induced echo of supernova remnants

    Yitian Sun🇺🇸 · Katelin Schutz🇨🇦 · Anjali Nambrath🇺🇸 · Calvin Leung🇺🇸 · Kiyoshi Masui🇺🇸

    Axions are a theoretically promising dark matter (DM) candidate. In the presence of radiation from bright astrophysical sources at radio frequencies, nonrelativistic DM axions can undergo stimulated decay to two nearly back-to-back photons, meaning that bright sources of radio waves will have a counterimage ("gegenschein") in nearly the exact opposite spatial direction. The counterimage will be spectrally distinct from backgrounds, taking the form of a narrow radio line centered at $\nu =m_a/4\pi$ with a width determined by Doppler broadening in the DM halo, $\Delta \nu /\nu \sim 10^{-3}$. In this work, we show that the axion decay-induced echoes of supernova remnants may be bright enough to be detectable. Their non-detection may be able to set the strongest limits to date on axion DM in the $\sim 1-10\mu$eV mass range where there are gaps in coverage from existing experiments.

    hep-phastro-ph.GAastro-ph.HEPRD(2022)·29 citations
18. 18*

    Supercool Composite Dark Matter Beyond 100 TeV

    Iason Baldes🇧🇪 · Yann Gouttenoire🇮🇱 · Filippo Sala🇫🇷 · Géraldine Servant🇩🇪

    Dark Matter could be a composite state of a confining sector with an approximate scale symmetry. We consider the case where the associated pseudo-Goldstone boson, the dilaton, mediates its interactions with the Standard Model. When the confining phase transition in the early universe is supercooled, its dynamics allows for Dark Matter masses up to $10^6$ TeV. We derive the precise parameter space compatible with all experimental constraints, finding that this scenario can be tested partly by telescopes and entirely by gravitational waves.

    hep-phastro-ph.COJHEP(2022)·95 citations
19. 19*

    Thermal keV dark matter in a gauged B-L model with cosmic inflation

    Debasish Borah🇮🇳 · Suruj Jyoti Das🇮🇳 · Abhijit Kumar Saha🇮🇳

    We investigate the possibility of keV scale thermal dark matter (DM) in a gauged $B-L$ extension of the standard model with three right-handed neutrinos (RHN) and one vector like fermion in the context of cosmic inflation. The complex singlet scalar field responsible for the spontaneous breaking of $B-L$ gauge symmetry is non-minimally coupled to gravity and serves the role of inflaton. The keV scale vector like fermion DM gives rise to the possibility of warm dark matter, but it gets overproduced thermally. The subsequent entropy dilution due to one of the RHN decay can bring the thermal abundance of DM within the observed limit. The dynamics of both the DM and the diluter are regulated by the $B-L$ model parameters which are also restricted by the requirement of successful inflationary dynamics.We constrain the model parameter space from the requirement of producing sufficient entropy dilution to obtain correct DM relic, inflationary observables along with other phenomenological constraints. Interestingly, we obtain unique predictions for the order of lightest active neutrino mass ($m_{{\nu }_l}\lesssim 10^{-14}$ eV) as function of $B-L$ gauge coupling for keV scale DM. The proposed framework also explains the origin of observed baryon asymmetry from the decay of other two heavier RHN by overcoming the entropy dilution effect.

    hep-phastro-ph.COPRD(2022)·11 citations
20. 20*

    Controlling unwanted exponentials in lattice calculations of radiative leptonic decays

    Christopher Kane🇺🇸 · Davide Giusti🇩🇪 · Christoph Lehner🇩🇪 · Stefan Meinel🇺🇸 · Amarjit Soni🇺🇸

    Two important sources of systematic errors in lattice QCD calculations of radiative leptonic decays are unwanted exponentials in the sum over intermediate states and unwanted excited states created by the meson interpolating field. Performing the calculation using a 3d sequential propagator allows for better control over the systematic uncertainties from intermediate states, while using a 4d sequential propagator allows for better control over the systematic uncertainties from excited states. We calculate form factors using both methods and compare how reliably each controls these systematic errors. We also employ a hybrid approach involving global fits to data from both methods.

    ↳ hep-lathep-phPoS(2022)·8 citations
21. 21*

    A new Wilson Line-based classical action for gluodynamics

    Hiren Kakkad🇵🇱 · Piotr Kotko🇵🇱 · Anna Stasto🇺🇸

    We develop a new classical action that in addition to $\mathrm{MHV}$ vertices contains also ${\mathrm{N}}^{\mathrm{k}}\mathrm{MHV}$ vertices, where $1\le k\le n-4$ with $n$ the number of external legs. The lowest order vertex is the four-point MHV vertex -- there is no three point vertex and thus the amplitude calculation involves fewer vertices than in the CSW method and, obviously, considerably fewer than in the standard Yang-Mills action. The action is obtained by a canonical transformation of the Yang-Mills action in the light-cone gauge, where the field transformations are based on the Wilson line functionals.

    ↳ hep-thhep-phSciPost Phys.Proc.(2022)·1 citation
22. 22*

    QCD viscosity by combining the gradient flow and sparse modeling methods

    Etsuko Itou🇯🇵 · Yuki Nagai🇯🇵

    We give a new description to obtain the shear viscosity in QCD at finite temperature. Firstly, we obtain the correlation function of the renormalized energy-momentum tensor using the gradient flow method. Secondly, we estimate the spectral function from the smeared correlation functions using the sparse modeling method. The combination of these two methods looks promising to determine the shear viscosity precisely.

    ↳ hep-lathep-phnucl-thPoS(2022)·4 citations
23. 23*

    Vorticity and $\Lambda$ polarization in the microscopic transport model PACIAE

    Anke Lei🇨🇳 · Dujuan Wang🇨🇳 · Dai-Mei zhou🇨🇳 · Ben-Hao Sa🇨🇳 · Laszlo Pal Csernai🇳🇴

    We study the behavior of four types of vorticities in non-central Au+Au collisions at energies $\sqrt{S_{NN}}$ = 5--200 GeV using a microscopic transport model PACIAE. The results show that the vorticities decay faster at lower energy and smaller impact parameter. The non-monotonic dependence of the initial vorticities on the collision energies is reconfirmed and the turning point is 10-15 GeV for different vorticities. The global $\Lambda$ polarization at energies $\sqrt{S_{NN}}$ = 7.7--200 GeV is reproduced by introducing an energy density freeze-out criterion.

    ↳ nucl-thhep-phPRC(2021)·24 citations
24. 24*

    Machine learning spectral functions in lattice QCD

    S.-Y. Chen🇨🇳 · H.-T. Ding🇨🇳 · F.-Y. Liu🇨🇳 · G. Papp🇭🇺 · C.-B. Yang🇨🇳

    We study the inverse problem of reconstructing spectral functions from Euclidean correlation functions via machine learning. We propose a novel neural network, SVAE, which is based on the variational autoencoder (VAE) and can be naturally applied to the inverse problem. The prominent feature of the SVAE is that a Shannon-Jaynes entropy term having the ground truth values of spectral functions as prior information is included in the loss function to be minimized. We train the network with general spectral functions produced from a Gaussian mixture model. As a test, we use correlators generated from four different types of physically motivated spectral functions made of one resonance peak, a continuum term and perturbative spectral function obtained using non-relativistic QCD. From the mock data test we find that the SVAE in most cases is comparable to the maximum entropy method (MEM) in the quality of reconstructing spectral functions and even outperforms the MEM in the case where the spectral function has sharp peaks with insufficient number of data points in the correlator. By applying to temporal correlation functions of charmonium in the pseudoscalar channel obtained in the quenched lattice QCD at 0.75 $T_c$ on $128^3\times 96$ lattices and $1.5$ $T_c$ on $128^3\times 48$ lattices, we find that the resonance peak of ${\eta }_c$ extracted from both the SVAE and MEM has a substantial dependence on the number of points in the temporal direction ($N_{\tau }$) adopted in the lattice simulation and $N_{\tau }$ larger than 48 is needed to resolve the fate of ${\eta }_c$ at 1.5 $T_c$.

    ↳ hep-latcs.LGhep-phhep-th+134 citations
25. 25*

    Roberge-Weiss transitions at imaginary isospin chemical potential

    Amine Chabane🇩🇪 · Gergely Endrödi🇩🇪

    At finite imaginary values of the chemical potential, QCD is free of the sign problem. Moreover, at high temperatures the partition function exhibits a new symmetry (the Roberge-Weiss symmetry) connecting phases with different orientations of the Polyakov loop, and the corresponding phase transitions between these. In this contribution we investigate the perturbative one-loop effective potential for the Polyakov loop in the presence of imaginary isospin as well as baryon chemical potentials. This leads to a novel phase diagram, which reveals an interesting insight about the rich phase structure of the system and the center symmetry breaking. We check the perturbative results using direct lattice simulations.

    ↳ hep-lathep-phPoS(2022)·4 citations
26. 26*

    Observation of non-linearity of generalized King plot in the search for new boson

    Koki Ono🇯🇵 · Yugo Saito🇯🇵 · Taiki Ishiyama🇯🇵 · Toshiya Higomoto🇯🇵 · Tetsushi Takano🇯🇵 · Yosuke Takasu🇯🇵 · Yasuhiro Yamamoto🇵🇱 · Minoru Tanaka🇯🇵 · Yoshiro Takahashi🇯🇵

    We measure isotope shifts for neutral Yb isotopes on an ultranarrow optical clock transition ${}^1{\text{S}}_0{-}^3{\text{P}}_0$ with an accuracy of a few Hz. The part-per-billion precise measurement was possible by loading the ultracold atoms into a three-dimensional magic-wavelength optical lattice and alternately interrogating the isotope pairs, thus minimizing the effects due to the optical lattice light-shift and inter-atomic interaction as well as the drifts of a clock laser frequency and a magnetic field. The determined isotope shifts, combined with one of the recently reported isotope-shift measurements of Yb${}^{+}$ on two optical transitions, allow us to construct the King plots. Extremely large nonlinearity with the corresponding ${\chi }^2$ on the order of $10^4$ is revealed, and is not explained by a quadratic field shift. We further carry out the generalized King plot for three optical transitions so that we can eliminate the contribution arising from a higher-order effect within the Standard Model which might explain the observed nonlinearity of King plots for two transitions. Our analysis of the generalized King plot shows a deviation from linearity at the 3$\sigma$ level, indicating that there exist at least two higher order contributions in the measured isotope shifts. Then, under the reasonable assumption to attribute them to higher-order field shifts within the Standard Model, we obtain the upper bound of the product of the couplings for a new boson mediating a force between electrons, and neutrons $|y_e{y}_n|/(\hslash c)<1\times 10^{-10}$ for the mass less than 1 keV with the 95% confidence level is derived, providing an important step towards probing new physics via isotope-shift spectroscopy.

    ↳ physics.atom-phhep-exhep-phnucl-exPRX(2022)·46 citations
27. 27*

    Evaporating primordial black holes, the string axiverse, and hot dark radiation

    Marco Calzà🇵🇹 · John March-Russell🇬🇧 · João G. Rosa🇵🇹

    We show that primordial black holes (PBHs) develop non-negligible spins through Hawking emission of the large number of axion-like particles generically present in string theory compactifications. This is because scalars can be emitted in the monopole mode ($l=0$), where no angular momentum is removed from the BH, so a sufficiently large number of scalars can compensate for the spin-down produced by fermion, gauge boson, and graviton emission. The resulting characteristic spin distributions for $10^8$-$10^{12}$ kg PBHs could potentially be measured by future gamma-ray observatories, provided that the PBH abundance is not too small. This yields a unique probe of the total number of light scalars in the fundamental theory, independent of how weakly they interact with known matter. The present local energy density of hot, MeV-TeV, axions produced by this Hawking emission can possibly exceed ${\rho }_{\mathrm{CMB}}$. Evaporation constraints on PBHs are also somewhat weakened.

    ↳ astro-ph.COgr-qchep-phPRL(2024)·57 citations
28. 28*

    Searching for Axion-Like Particles with the Blazar Observations of MAGIC and Fermi-LAT

    Hai-Jun Li🇨🇳 · Xiao-Jun Bi🇨🇳 · Peng-Fei Yin🇨🇳

    We explore the axion-like particle (ALP)-photon oscillation effect in the $\gamma$-ray spectra of the blazars Markarian 421 (Mrk 421) and PG 1553+113, which are measured by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) and Fermi Large Area Telescope (Fermi-LAT) with high precision. We investigate the constraints on the ALP parameter space using the Mrk 421 and PG 1553+113 observations of 15 and 5 phases, respectively. We find that the combined analysis with all the 15 phases improves the limits from the Mrk 421 observations. The combined limit set by the Mrk 421 observations has excluded the ALP parameter region with the ALP-photon coupling of $g_{a\gamma }\gtrsim 2\times 10^{-11}\mathrm{Ge}{\mathrm{V}}^{-1}$ for the ALP mass of $\sim 8\times 10^{-9}\mathrm{eV}\lesssim m_a\lesssim 2\times 10^{-7}\mathrm{eV}$ at 95% $C.L.$ We also find that the ALP hypothesis can slightly improve the fit to the PG 1553+113 results in some parameter regions, and do not set the limit in this case.

    ↳ astro-ph.HEhep-phCPC(2022)·40 citations
29. 29*

    The two-loop bispectrum of large-scale structure

    Tobias Baldauf🇬🇧 · Mathias Garny🇩🇪 · Petter Taule🇩🇪 · Theo Steele🇬🇧

    The bispectrum is the leading non-Gaussian statistic in large-scale structure, carrying valuable information on cosmology that is complementary to the power spectrum. To access this information, we need to model the bispectrum in the weakly non-linear regime. In this work we present the first two-loop, i.e., next-to-next-to-leading order perturbative description of the bispectrum within an effective field theory (EFT) framework. Using an analytic expansion of the perturbative kernels up to $F_6$ we derive a renormalized bispectrum that is demonstrated to be independent of the UV cutoff. We show that the EFT parameters associated with the four independent second-order EFT operators known from the one-loop bispectrum are sufficient to absorb the UV sensitivity of the two-loop contributions in the double-hard region. In addition, we employ a simplified treatment of the single-hard region, introducing one extra EFT parameter at two-loop order. We compare our results to N-body simulations using the realization-based grid-PT method and find good agreement within the expected range, as well as consistent values for the EFT parameters. The two-loop terms start to become relevant at $k\approx 0.07h{\mathrm{Mpc}}^{-1}$. The range of wavenumbers with percent-level agreement, independently of the shape, extends from $0.08h{\mathrm{Mpc}}^{-1}$ to $0.15h{\mathrm{Mpc}}^{-1}$ when going from one to two loops at $z=0$. In addition, we quantify the impact of using exact instead of Einstein-de-Sitter kernels for the one-loop bispectrum, and discuss in how far their impact can be absorbed into a shift of the EFT parameters.

    ↳ astro-ph.COhep-phPRD(2021)·41 citations

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